Electrical connecting means and radio shielding means therefor



J. R. FREI Aung. 13, 1946.

ELECTRICAL CONNECTING MEANS AND RADIO SHIELDI'NG MEANS THEREFR Filed. May 6, 1941 INVENTOR ATTORNEY Patented Aug. 13, 1946 ELECTRICAL CNNECTING MEANS AND RADIO SHIELDING MEANS THERE- FOR i Jakob R. Frei, Sidney, N. Y., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application May 6, 1941, Serial No. 392,032

14 Claims.

This invention relates to electrical apparatus, and more particularly to electrical connector means adapted for use in a radio shielded ignition system of an internal combustion engine.

In spite of the fact that radio-shielding has been considered an essential part of ignition systems on aircraft engines for many years, and in spite of the fact that the connection between the shielded high tension supply cable and the shielded spark plug has long been recognized as the weakest link in such systems, no truly satisfactory connector for this purpose has been heretofore devised, although innumerable attempts have been made to solve this diicult problem in a practical manner.

It is accordingly an object of this invention to provide a novel and practical connector of the above character.

Another object of the invention is to provide a novel insulating member which is associated in a novel manner with an electrical conductor and radio-shielding means therefor.

Still another object is to provide insulating means for an electrical conductor which is so constlucted as to cooperate in a novel manner with a radio-shielding conduit for said conductor and the radio-shield of a spark plug.

A further object is to provide novel insulated conductor means for electrically connecting a pair of conductors of high tension electrical n current.

A still further object is to provide novel means for electrically connecting a high tension insulated cable to the center electrode of a radio shielded spark plug whereby the cable insulation is protected from the deleterious effects of high temperatures, hot gases and moisture,

Another object is to provide novel plug and socket connecting means for electrically connecting high tension electrical conductors whereby good electrical contact between the conducting parts is obtained and the possibility of arcing between the high tension conductors and the connecting means is reduced to a minimum.

The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawing. It is to be expressly understood, however, that the drawing is for the purpose of illustration only and is not intended as a definition of the limits of the invention, reference for this latter purpose being had primarily to the appended claims.

In the drawing, wherein like reference characters refer to like parts throughout the several views,

Fig. l is a full size side elevation, partly in section and with parts broken away, of apparatus embodying one form of the present invention;

Fig. 2 is an enlarged detail view, partly in section and with parts broken away, showing the plug portion of the connector of the apparatus of Fig. 1;

Figs. 3 and 4 are enlarged detail views, partly in section and with parts broken away, illustrating other embodiments of the insulated connector constituting a part of the present invention and adapted for use in the apparatus of Fig. 1; and,

Fig. 5 is a View similar to Fig. 2 of another embodiment of the plug portion of a connector.

The embodiment of the invention shown, by way of example, in Fig. 1 of the drawing is illustrated in conjunction with a shielded spark plug 5 of the type now in almost universal use on aircraft engines. Said spark plug may be of any suitable internal construction and comprises a center electrode 6 which is insulated from the outer shell or casing I 8 which includes a shielding barrel or socket 9 that surrounds and extends beyond the upper end of said electrode and is lined with a tube of electrical insulating material I0, such as sheet mica. The upper portion of barrel 9 is externally threaded at I I for a purpose to appear hereafter.

For the purpose ofconducting high tension electrical current to electrode 6 of the spark plug there is provided an insulated cable I2, the conducting portion I3 of which is preferably constituted by several strands of stainless steel or other suitable conducting material. 'Ille insulation I4 on said cable is preferably constituted by a material which will resist the deleterious effects of high temperatures, such as an insulation having a base of polymerized cashew nut shell oil. Cable I2 is encased in a metallic conduit I5 to obviate the radiation of electrical disturbances which interfere with radio reception. Said conduit may comprise a flexible portion I6, a rigid elbow I1 and a ferrule I8, said parts being secured together by any suitable means, such as soldering or brazing. In order to removably secure the shielded conduit to spark plug barrel 9, ferrule I8 is preferably provided with an external liange I9 for cooperation with an internally threaded coupling nut 20 which also cooperates with threaded portion II of said barrel. The space within conduit portions I6 and II, around cable I2, is preferably filled with a suitable solid insulating material 2| which serves to prevent vibration of the cable relative to the conduit and to prevent any accumulation of moisture in the conduit by condensation or otherwise. The filling material also prevents any substantial axial movement of cable I2 relative to the shielding conduit and may consist of polymerized cashew nut shell oil. This material may be inserted in the conduit in liquid form and permitted to set through chemical reaction without appreciable shrinkage.

Novel means adapted to slidably extend into socket 9 are provided for electrically connecting conductor l2 to center electrode or conductor E of the spark plug, for spacing exposed portions of the high tension conductors from the grounded portions of the radio shielding parts a suicient distance to prevent flash-overs under normal opn erating conditions and for protecting that portion of cable I2 which projects from elbow I'I from the deleterious efects of high temperatures, hot gases which may leak through the spark plug insulation, electrical arcing from the high tension conductors to grounded portions of the shielded parts, and moisture. Said novel means in the form shown in Figs. l and 2 comprise a cylindrical sleeve or tube 22 of insulating material, such as molded ceramic, Melmac (a synthetic resin) or the like, which is capable of withstanding high temperatures and rough usage and has a high resistance to carbonization under arcing conditions. The upper portion of the bore in sleeve 22 is preferably just large enough to slidably receive the end of insulated cable I2 which projects from conduit I and the lower portion thereof may be slightly enlarged for receiving a hollow metallic member 23, the latter being closed at its upper end and having a pointed projection or spike 24 adapted for abutting engagement with stranded conductor I3 at the end of cable I2. Cup-shaped member 23 is iitted into the bore of tube 22 andheld therein in substantially gas-tight relation with the walls of said tube by cement or other suitable means. If cement is used for this purpose, the outer surface of member 23 may be provided with shallow annular or helical grooves or the like to enhance the effectiveness of the cement as a retaining and sealing medium.

A contact pin 25, having a ball-like portion 2G at its lower end and a piston-like portion 2l at its upper end, is slidably mounted in the hollow or recessed part of member 23 and projects from tube 22 for yieldable electrical contact with center electrode 6. Suitable means are provided for limiting the outward movement of contact member 25 and, in the form shown, such means is constituted by a washer 28 held in member 23 by spinning the edge of the latter inwardly. Interposed between the closed end of member 23 and contact pin 25 is a compression spring 2S which normally holds said pin in extended position (Fig. 2) and is adapted to insure goed electrical contact between ball 25 and electrode 5 when the plug and socket portions of the invention are assembled (Fig. l). The parts 23, 25 and 29 thus constitute axially yieldable means for electrically connecting conductors 6 and I3, said means having abutting engagement with said conductors to facilitate disassembly of the parts.

It is highly desirable that the insulating sleeve 22 be operatively secured to conduit I5 for removal therewith from spark plug 5 and yet be readily removable from said conduit for purposes of inspection and replacement. At the same time a sufficiently good contact between the conduce tors 6 and I3 and the connecting means therefor to obviate arcing therebetween must be assured. To this end, therefore, insulating tube 22 and ferrule I8 of conduit I5 are operatively connected in a novel manner. Said ferrule is provided with a small number of internal threads 30 which are adapted tc cooperate with external threads 3I on the upper end of molded tube 22. The inner diameter of ferrule I8 interiorly of threads 30 is sufciently large to accommodate the threaded portion of tube 22 so that the latter may be freely rotated relative to the shielding conduit when the cooperable threads are disengaged and may be moved axially relative to said conduit to insure good electrical contact between cable I2 and member 23 when the parts of the apparatus are assembled and to obviate placing said tube under a stress which might cause the same to crack. rThis relative axial movement may be limited to the diiierence between the axial extent of threads 3| and the distance between threads 3d and a shoulder 32 within ferrule I8. Preferably, however, said axial movement is limited to the diiference between the axial extent of threads 30 and the distance between threads 3i and an anN nular shoulder 33 which is formed integrally with tube 22.

Although annular shoulder 33 is not absolutely necessary, the same is preferably provided for `the purpose of xing tube 22 against movement relative to barrel S and conduit I5 when the parts are in assembled relation. Said shoulder may be covered with a gasket 34 of copper or other suitable material and is adapted to extend between the adjacent ends of said conduit and barrel. Cable I2 .preferably projects from the shielding conduit a sufficient distance so that it engages member 23, 24 just prior t0 the engagement of ferrule I3 and shoulder 33, 34 (Fig. 2) so that when coupling nut 25 is screwed home (Fig. l) to rmly clamp said shoulder between the ends of barrel il and ferrule i8 the cable will be placed under some compression and may buckle slightly, thereby insuring good electrical contact even though the cable may shrink soma what under the action of the hea-t during use.

Securing the parts together in the above manner also results in the provision of a seal at shoulder 33, 34 against the entrance of moisture from outside the shielding means and against any leakage of hot gases from the spark plug well into the space within ferrule I8 around cable l2 and insulating tube 22. The seal thus provided is effected without subjecting the insulating material of tube 22 to any twisting moments or strains which might cause breakage thereof. Vibration of the insulating tube relative to the spark .plug is also avoided by clamping the tube in position.

In order to further insure against arcing or flash-overs between terminal 26 and the internally exposed metal at the upper end of barrel 9 and between the end of cable l2 and metallic conduit I5, the annular spaces 35 and 36 between tube 22 and barrel 9 and between cable I2 and said tube, respectively, may be sub-stantially illed with a viscous insulating material, such as Tite Seal, which is a mixture comprising castor oil and mica powder and having the consistency of grease. This material also avoids the formation of moisture paths along the insulating materials which might promote flash-overs between the high tension conducto-rs and the grounded metallic parts.

rIhe embodiment illustrated in Fig, 3 differs from that above described in that spike 24 is replaced by a spirally coiled spring 31. The latter has the largest turn thereof interposed and clamped between member 23 and an internal shoulder 38 in the bore of insulating tube 22. When this embodiment is used, good electrical contact with conductor i3 is doubly insured. In order to prevent any possible catching between conductor I3 and spring 3l, a tack 39 with a smooth, enlarged head may be stuck into the end of cable l2.

In the modiiication illustrated in Fig. 4, an open-ended cylinder 4D is provided in lieu of member 23 of Fig. 1. lIhe upper end of said cylinder is closed by a cup-like member 4| having an external ange or bead 42 at the open end thereof which is slidable in the cylinder and retained therein by an internal iiange 43. A co-m- .pression spring 44 is interposed between member 4l and contact plunger 25, thereby providing yielding contact means for both conductors 6 and i3, Member 4| may, of course, be replaced by a plunger similar to plunger 25 or by any other suitable equivalent structure.

In Fig. 5 there is illustrated still another embodiment of the plug portion of the connector in which an insulating spacer sleeve 22a is removably mounted by means of cooperating screw threads in a metallic ferrule [8a that is secured to metallic shielding elbow Il to form a shielding conduit. The cooperating screw threads on parts |8a and 22a are coextensive and the latter is screwed home, so to speak, in the ferrule so that the upper end of the insulating tube or sleeve engages an internal shoulder 32a of the shielding conduit to thereby form a gas-tight seal and prevent the leakage of gases and moisture from the spark plug well into the space around cable l2. When this embodiment is assembled with a spark plug 5 (Fig. l), the lower face of flange Illa is pressed into sea-ling engagement with the upper end of shielding barrel 8 by nut 23, thus obviating any strains or stresses on insulating tube 22a. Any suitable electrical conducting means may be provided in the lower end of tube 22a, the means shown being identical with that illustrated in Fig. 3.

There is thus provided novel means for electrically connecting radio shielded conductors of high tension electrical current whereby such connection and the connection of the shielding means therefor may be readily and quickly effected and whereby good electrical connections are assured. Novel means of the above character are also provided whereby the effects of high temperatures, moisture, arcing and rough handling are eilectively minimized. A novelly constructed insulating and spacer sleeve adapted for use in connecting means of the above character is also combined in a novel manner with radio shielding means for high tension conductors whereby said sleeve may be readily installed or removed for inspection or replacement in the field without the aid of tools of any kind. Said spacer sleeve is also combined in a novel manner with yieldable means for eecting an electrical connection between two high tension conductors, the parts being so constructed and assembled that no mechanical connections to the spark plug ends of the shielding harness cables are necessitated.

Although only a limited number of modifications of the invention are illustrated and described, it is to be expressly understood that the same is not limited thereto. be adapted to other applications, and the arrangement and design of the parts may be varied with- The invention may out departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art. For a denition of the limits of the invention, reference is had primarily to the appended claims.

What is claimed is:

l. In apparatus of the class described a metallic socket lined with electrical insulating material and having an electrical conductor therein, a radio shielding conduit, means for securing said socket and conduit together in axial alignment with each other, a tube of electrical insulating material removably mounted in said conduit and slidably extending into said socket, said tube having an enlarged annular portion interposed between and in sealing relation with the adjacent ends of said conduit and socket, an insulated electricalr conductor extending through said conduit into said tube, means in said conduit for holding said insulated conductor against substantial axial movement relative thereto, a hollow metallic member filling a portion of the bore in said tube at the end of the latter within said socket, the closed end of said member being adjacent said insulated conductor and having abutting electrical contact therewith, resilient means in said member, a contact plunger slidably mounted in said member and interposed between said resilient means and the conductor in said socket, and cooperable screw threads on said tube and in said conduit, said threads being disengaged when the conduit and tube are assembled to thereby permit limited axial movement of the tube relative to the conduit.

2. In connector means for radio-shielded conductors of high tension electrical current, a metallic conduit, an electrical insulating tube projecting from one end of said conduit and removable therefrom through said end, and cooperable means integral with said conduit and tube for normally retaining the end of said tube in said conduit while permitting rotational and limited axial movements of said tube relative to the conduit, said rotational and axial movements being adapted to take place independently of each other.

3. In connector means for radio-shielded conductors of high tension electrical current, a radio shielding conduit, an insulated electrical conductor in said conduit, means in said conduit for xing said conductor against substantial movement relative thereto, a tube of insulating material extending into the end of said conduit and surrounding a projecting portion of said conductor, and means including cooperable screw threads on said tube and in said conduit for removably retaining an end of said tube in said conduit independently of said conductor, said screw threads being out of cooperating screw-thread engagement when said tube and conduit are assembled.

4. In apparatus ci the class described, a pair of axially aligned radio shielding conduits, an

electrical conductor xed in and insulated from each of said conduits, the end or" one of said conductors projecting from one of said conduits into the other of said conduits, means for securing said conduits together, a sleeve of insulating material removably mounted in said one conduit for free angular movement and limited axial movement relative thereto and slidably extending into said other conduit, said sleeve loosely surrounding said projecting end of the conductor and said axial movement being independent of said angular movement, and axially yieldable means having abutting engagement with said conductors for electrically connecting the same.

5. A radio shielded plug and socket connector for high tension electrical conductors comprising a metallic socket having an insulating lining and a conductor therein, a plug adapted to cooperate with said socket comprising a metallic conduit having an electrical conductor therein, said lastnamed conductor projecting from said conduit, an insulating tube surrounding the projecting portion of said last-named conductor and having a portion intermediate its ends disposed between said socket and conduit, means for removably securing said tube in said conduit for limited axial movement relative thereto, and axially yieldable means mounted in the bore of said tube in abutting contact with said conductors for electrically connecting the latter, and means for securing said conduit to said socket.

6. Insulated connector means for radio shielded conductors of high tension electrical current Comprising an .insulating tube having a differential bore therein, a recessed conducting member mounted in the larger portion of said bore in substantially gas-tight relation with the walls thereof, a spiral coil spring in the smaller portion of said bore and having a portion thereof securely clamped between said member and an internal shoulder in said tube, plunger means slidable in the recess of said member and projecting from one end of said tube, means for limiting the movement of the plunger means out of said tube, and resilient means in said recess for yieldably resisting movement of said plunger means into said tube.

7. In apparatus of the class described, a tube of insulating material, a recessed electrically conducting member mounted in the bore of said tube, a coil spring in said bore having a portion at one end thereof securely clamped between the closed end of said member and an internal shoulder in said tube, and a spring pressed contact plunger slidably mounted in the recess in said member.

8. In combination with a spark plug having a center electrode and a shielding barrel surrounding the upper end of said electrode, a metallic radio shielding conduit, an insulating tube extending from said conduit into said barrel, an enlarged annular portion or" said tube being disposed between and engageable with the adjacent ends of said conduit and barrel, screw threads on said tube, screw threads in said conduit adapted to cooperate with said rst-named threads and normally disposed between the latter and said annular portion, whereby said tube may have limited axial movement relative to said conduit, an insulated conductor extending from said conduit into said tube, axially yieldable means mounted in said tube for electrically connecting said conductor and said electrode, and means engaging said conduit and barrel for securely clamping said annular portion therebetween.

9. In connector means for radio-shielded conductors of high tension electrical current, a radio-shielding conduit for an insulated electrical conductor, means in said conduit for fixing said conductor against substantial movement relative thereto, a tube of insulating material extending into one end of said conduit and surrounding a projecting portion or" said conductor, cooperable means formed integrally with said tube and conduit for removably securing said tube in said conduit independently of said conductor, electrical conducting means sealing the bore of said tube adjacent the outer end thereof in a substantially gas-tight manner, and axially yieldable conducting means interposed between said first-named conducting means and said conductor.

10. In apparatus of the class described, a metallic socket lined with electrical insulating material and having an electrical conductor therein, a metallic conduit, means for securing said socket and conduit together in axial alignment with each other, a tube of electrical insulating material removably mounted in said conduit and slidably extending into said socket, said tube having an enlarged annular portion interposed between and in sealing relation with the adjacent ends of said conduit and socket, an insulated electrical conductor extending through said conduit into said tube, a hollow metallic member iilling a portion of the bore in said tube adjacent the end of the latter within said socket, the closed end oi said member being adjacent said insulated conductor, yieldable means interposed between said member and insulated conductor for electrically connecting the same, resilient means in said member, a contact plunger slidably mounted in said member and interposed between said resilient means and said first-named conductor, and cooperable means on said conduit and tube for removably retaining the end of said tube in said conduit while permitting rotary and limited axial movements or said tube relative to said conduit.

l1. In apparatus of the class described, a metallic socket lined with electrical insulating material and having an electrical conductor therein, a metallic conduit, means for securing said socket and conduit to each other, a tube comprising electrical insulating material removably mounted in said conduit and slidably extending yinto said socket, said tube having an enlarged external portion interposed between and in sealing relation with adjacent end portions of said conduit and socket, an insulated electrical conductor extending from said conduit into said tube, an electrically conducting member filling a portion of the bore of said tube and being in substantially gas-tight relation with the walls thereof, separate yieldable means at opposite ends of `said member for electrically connecting said member with said conductors, and cooperable means `on said conduit and tube for removably retaining the end of said tube in said conduit while permitting rotary and axial movements of said tube relative to said conduit.

l2. Connector means for radio-shielded conductors of high tension electrical current comprising an electrical insulating tube, a recessed conductor member mounted in the bore of said tube in substantially gas-tight relation with the walls thereof, resilient means secured within said ,bore and having electrical contact with a portion of said member nearest one end of said tube, plunger means slidable in the recess of said member and projecting from the other end of said tube, means for limiting the movement of the plunger means out of said member, resilient means in said recess for yieldably resisting movement of said plunger means into said member, a metallic conduit for receiving said one end of said tube, an insulated conductor extending from said conduit into said tube for engagement with said first-named resilient means, and means in said conduit for xing said conductor against 'appreciable longitudinal movement relative to said i conduit.

13. In apparatus of the class described, a tube of electrical insulating material, an electrically conducting member having a recess in one end thereof mounted in the bore of said tube in substantially gas-tight relation with the Walls therecf, yieldable means secured Within said bore and having electrical contact with the end of said member opposite said recess, a spring pressed contact plunger slidably mounted in said recess and projecting from said tube, a metallic conduit for receiving an end portion of said tube, an insulated conductor extending from said conduit into said tube for electrical contact with said yieldable means, and means in said conduit for fixing said conductor against appreciable movelic conduit, an electrical insulating tube projectying from one end of said conduit, cooperable means integral with said conduit and tube for normally retaining an end of said tube in said `conduit While permitting rotational and limited axial movements of said tube relative to the conduit, said rotational and axial movements being independent of each other, a metallic socket for "receiving the projecting end of said tube, the latter having an enlarged annular portion thereof .interposed between adjacent surfaces of said conduit and socket, and means for securing said ccn- Vduit and socket together for holding said surfaces in sealing engagement with Said enlarged portion.

JAKOB R. FREI. 

